Birding Picacho Reservoir, Pinal County, Arizona

By Cliff Drowley, Maricopa Audubon Society

Picacho Reservoir is a rarity in central Arizona: a marshy oasis in the midst of an arid cotton-growing region. The lake draws waterfowl and shorebirds, and attracts unusual vagrants. The reservoir is less than 60 miles from both the Phoenix and Tucson areas. Despite its proximity, the reservoir has been a somewhat obscure destination for Phoenix birders; this article is intended to serve as a guide for MAS members and others who may wish to visit the area.

Background 

The reservoir was built in the 1920's as part of the San Carlos Irrigation Project. The reservoir's original purpose was water storage and flow regulation for the Florence-Casa Grande and Casa Grande Canals. The lake's design capacity was 24,500 acre-feet of water, with a surface area of over 2 square miles.Map 1

Over the years, siltation and vegetation have reduced the capacity and surface area, so that much of the reservoir is a shallow marsh with extensive stands of cattails and rushes. Water level is highly variable, and the lake is completely dry in some years.

Turn east onto the Selma Highway (which becomes a dirt road) (Map 2). Continue on the Selma Highway 1 mile east to a T intersection in front of some electrical equipment and an embankment. Turn right (south) and go 0.3 mile to a canal road; turn left and follow the canal about 0.6 mile. The reservoir levee will be in front of you; take the road up the levee. This is the "southwest corner" of the reservoir, with a view over the main body of the lake. The tour continues counterclockwise around the reservoir from here (see Map 2).

If the water is low, you can drive down into the lakebed from the levee at the southwest corner; park here and walk toward the water for closer views (if the lake is full, park on the wider section of the levee to the north). The mud is passable if it has dried on the surface; watch your footing. The lake has dead snags in it, in addition to large stands of cattails and reeds. Scan the mudflats for shorebirds, terns and gulls; check the cattail clumps for rails. The snags often hold perched cormorants and herons, in addition to raptors and terns (in migration). Check the sky for Osprey and other raptors.

The spillway is about 0.2 mile north of the SW corner; walk the levee to the spillway and scan the cattail beds. Sora and other rails may be seen; Common Yellowthroat are fairly common in spring . Check for Marsh Wren as well.

The Grand Tour 

Return to the levee road at the SW corner, and drive east along the levee road, scanning the lake and marsh. Tamarisk (salt cedar) thickets appear on the lakebed and along the levee bank.

A number of roads lead north into the lakebed from the levee; these are passable at low water. Each road provides slightly different views of the lake and marsh. Use caution in driving these roads; deep mud is common after rains or when the water is high, and ruts are common when the roads are dry. A high clearance vehicle is recommended. When in doubt, walk instead of drive; always check your footing. The first road (marked "A" on map 2) is about 0.6 mile from the SW corner, and leads about 0.3 mile north. The second road (marked "B") is about 0.1 mile further on, and also leads north about 0.3 mile. A third road (marked "C") starts at about 0.95 mile from the SW corner, and leads to the SE corner of the lakebed. This road ends at mudflats, which can be followed for over half a mile; again, use judgement on mud conditions.

The levee road continues generally east. The adjacent reservoir bed becomes shallower with increasing tamarisk growth. About 1.6 miles from the SW corner, the road reaches a junction (the "southeast corner" on map 2). A bridge crosses the canal to the south, and a major road heads NNE along the canal. A minor, single-lane road (marked "D") heads due north on a levee through a mesquite bosque just west of an overgrown ditch. This road continues on the levee for 0.5 mile, at which point it drops off the levee and heads generally west toward the lake. At low water, this road may be followed for over 0.5 mile to access the north shore of the lake. Again, use caution; the top of the levee may be under water at highest water, there is almost no room to turn around on the levee, and part of the road from the levee toward the lake is in a wash (dangerous during rains).

Returning to the SE corner, take the road NNE along the canal.

This road has a stand of mesquite along the left (west) side, with a similar stand across the canal to the east. Species such as Bell's Vireo and Lucy's Warbler may be seen here in spring and summer, and Pyrrhuloxia and Cardinal are both found along the road. Phainopepla also frequent the mesquites. The road is wide enough to park along the shoulder and walk.

Occasional passages break through the mesquite to the west, into an open area. Thrashers and Abert's Towhee may be found along the edge of the open space, and Gambel's Quail are common. Ladder-backed and Gila Woodpeckers may be found in the mesquites. From fall through early spring, wintering sparrows may be found, including Lark Sparrow and Vesper Sparrow.

The road continues generally north along the canal for about 2.9 miles before crossing a large floodgate. This gate is the main feeder for the reservoir; water may be sent down a channel heading WSW toward the lake. Just before the floodgate, a road heads SW (marked "E") into the open region which may be birded for arid-scrub species. Just past the floodgate, the road around the reservoir turns WSW, while the canal road continues north. This is the "northeast corner". Turn left (WSW) to continue on the reservoir road.

The road parallels the feeder channel for about 0.4 mile, at which point the channel turns more southerly, and the road veers toward the west. Fields appear to the north and west. In another 0.8 mile, a willow "gallery" appears for about 0.2 mile along the left (south) side of the road. This area may be birded for riparian and migrant passerines. The road reaches a junction with a frontage road along the levee at 0.4 miles beyond the willow gallery (1.8 miles from the NE corner). Continue on the levee road; large salt cedars appear to the west and continue off and on for the next 0.9 mile. These may be birded for migrant warblers and other passerines. The road turns due south at about 2.1 miles from the NE corner. The area inside the levee is mostly tamarisk; this is good habitat for ducks in winter when flooded (bird from the road if flooded!).

About 3 miles from the NE corner, the road reaches the headgate for the Casa Grande canal ("F" on map 2). The canal can be seen below the levee, headed north. Just before the headgate, a road goes east off the levee into the lakebed, starting near a large cottonwood. This road may be followed for over 0.5 mile, water level permitting, through several large stands of reeds and cattails, which may be seen from the levee. At low water, this road accesses the western shore of the lake and marsh.

The levee road continues south from the canal headgate another 0.4 mile, before dropping off the levee to pass in front of the spillway. The road in front of the spillway is basically crossing a shallow wash, and may be impassable if water is running (or has been running recently); use caution. The road returns to the levee 0.1 mile past the spillway, and returns to the starting point at the SW corner in another 0.2 miles.

Total distance around the reservoir is about 8.3 miles.